Fuel supply apparatus and fuel supply method

ABSTRACT

The temperatures of fuel oils stored in fuel tanks  12   a,    12   b,    12   c  are separately detected by temperature sensors  52   a,    52   b,    52   c,  respectively. Based on the detection results, a CPU  49  heats a heat resistant fuel oil among the fuel oils using a heat exchanger  54,  such that the temperature of an oil mixture generated by mixing the fuel oils satisfies a predetermined temperature condition. After the fuel oils including the heated heat resistant fuel oil are mixed in a blender  13,  the CPU  49  detects the viscosity of the generated oil mixture using a viscometer  33.  Thereafter, based on the detection result, the CPU  49  controls the mixture ratio or a heating temperature of the heat resistant fuel oil, such that the viscosity of the oil mixture satisfies a predetermined viscosity condition.

TECHNICAL FIELD

The present invention relates to a fuel supply apparatus and a fuelsupply method for supplying as fuel an oil mixture made by mixingvarious types of oils.

BACKGROUND ART

In recent years, the increase in performance of diesel engines hasenabled oil mixture to be used as fuel other than light oils or heavyoils, which are used alone. The oil mixture refers to a type of oil madeby mixing multiple types of oils having different viscosities.Accordingly, inexpensive low-quality oil having a viscosity higher thanthat of high-quality oil such as light oil has been selected as amaterial of the oil mixture. This reduces fuel costs.

For such an oil mixture, not only oils having low viscosities, but alsooils having high viscosities are used as materials, taking intoconsideration the prices of the fuels. To use oil mixture as fuel, theviscosity of the oil mixture itself is adjusted. For example, PatentDocument 1 discloses a fuel supply apparatus for supplying oil mixtureas described above to an engine. In this fuel supply apparatus, theviscosity of oil mixture, which has been generated by mixing variousoils, is detected in a supply passage for supplying the oil mixture toan engine. Based on the detection result, the oil mixture is heated inthe supply passage leading to the engine to adjust the viscosity of theoil mixture, such that the viscosity becomes appropriate for use in adiesel engine.

However, in the above fuel supply apparatus, the oils constituting theoil mixture can include components that can be oxidized and degraded byheating the oil mixture to adjust the viscosity. Particularly, in recentyears, biodiesel fuel, which is obtained by refining plant-derived oiland waste edible oil, has received a lot of attention as a circulationtype energy. Use of oil mixture obtained by mixing these oils with lightoil or heavy oil has been proposed. However, in general, biodiesel fuelis easily oxidized and degraded by heat. Therefore, in the case wheresuch an oil mixture is used as fuel, degradation of the fuel due tooxidation generates polymer substances, which can clog filters.

Patent Document 1: Japanese Laid-Open Patent Publication No. 2005-127279

DISCLOSURE OF THE INVENTION

Accordingly, it is an objective of the present invention to provide afuel supply apparatus and a fuel supply method that keep the viscosityof fuel in a range of a predetermined condition, while suppressingdegradation of the fuel due to oxidation.

To achieve the foregoing objective and in accordance with a first aspectof the present invention, a fuel supply apparatus is provided thatincludes: mixing means for generating an oil mixture by arbitrarilycombining and mixing a plurality of types of fuel oils including a heatresistant fuel oil; fuel temperature detecting means for separatelydetecting temperatures of the fuel oils before the mixing means mixesthe fuel oils; heating means for heating only the heat resistant fueloil among the fuel oils before the mixing means mixes the fuel oils; andcontrol means for controlling, based on a detection result of the fueloil temperature detecting means, the heating means such that thetemperature of the oil mixture obtained by mixing the fuel oils becomesa temperature that is set in advance.

In accordance with this configuration, non-heat resistant fuel oil andheat resistant fuel oil are mixed after the heat resistant fuel oil isheated, without directly heating non-heat resistant fuel oil. Therefore,the viscosity of the oil mixture can be adjusted without degrading thenon-heat resistant fuel oil by oxidation of the non-heat resistant fueloil constituting the oil mixture with the heat resistant fuel oil.

The fuel supply apparatus preferably further includes viscositydetecting means for detecting a viscosity of the oil mixture generatedby the mixing means. Based on a detection result of the viscositydetecting means, the control means preferably controls a mixture ratioor a heating temperature of the heat resistant fuel oil that is heatedby the heating means, such that the viscosity of the oil mixture is keptin a viscosity range that is set in advance.

In accordance with this configuration, by detecting the viscosity of theoil mixture after the fuel oils are mixed, the feedback control can beperformed such that the viscosity of the oil mixture is kept in therange of the predetermined viscosity condition.

Also, the fuel supply apparatus preferably further includes: oil mixturetemperature detecting means for detecting a temperature of the oilmixture that is generated by mixing the fuel oils using the mixingmeans; and memory means for storing fuel maps each defining therelationship between a viscosity of the oil mixture and mixture ratiosof the fuel oils at each of different temperatures of the fuel oils.Based on a detection result of the oil mixture temperature detectingmeans and the fuel maps stored in the memory means, the control meanspreferably controls the mixture ratio or a heating temperature of theheat resistant fuel oil, such that the viscosity of the oil mixture iskept in a viscosity range that is set in advance.

In accordance with this configuration, after mixing the fuel oils, thefeedback control can be performed such that the viscosity of the oilmixture is kept in the range of the predetermined viscosity condition,based on the temperature detection result of the oil mixture and thefuel map set for each temperature condition of the oil mixture.

The fuel supply apparatus preferably further includes: a plurality offuel tanks each storing different one of the fuel oils; and a pluralityof supply passages each connected to different one of the fuel tanks.The heating means is preferably provided in the fuel tank that storesonly the heat resistant fuel oil or in the supply passage that suppliesonly the heat resistant fuel oil.

In accordance with this configuration, since only the heat resistant oilis heated, other non-heat resistant fuel oils are not oxidized anddegraded by heating.

In accordance with another aspect of the present invention, a fuelsupply method is provided that includes: fuel oil temperature detectingstep for separately detecting temperatures of a plurality of fuelincluding a heat resistant fuel oil; heating step for heating only theheat resistant fuel oil among the fuel oils based on a detection resultof the fuel oil temperature detecting step such that the temperature ofthe oil mixture obtained by mixing the fuel oils becomes a temperaturethat is set in advance; and mixing step for generating the oil mixtureby arbitrarily combining and mixing the fuel oils including the heatresistant fuel oil.

In accordance with this configuration, the same advantages as those ofthe above fuel supply apparatus are achieved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a system diagram schematically showing a fuel supply apparatusaccording to one embodiment of the present invention;

FIG. 2 is a block diagram illustrating a control device according to theembodiment of the present invention;

FIG. 3( a) is a fuel map showing the correspondence relationship amongthe mixture ratio of a vegetable oil and an A heavy oil, the viscosityof the oil mixture, and the temperature of the oil mixture; and

FIG. 3( b) is a fuel map showing the correspondence relationship amongthe mixture ratio of the fatty acid methyl ester and the A heavy oil,the viscosity of the oil mixture, and the temperature of the oilmixture.

BEST MODE FOR CARRYING OUT THE INVENTION

One embodiment of the present invention will now be described withreference to the drawings.

As shown in FIG. 1, a fuel supply apparatus 11 according to the presentembodiment includes first to third fuel tanks 12 a, 12 b, 12 c, ablender 13, and an engine 14 serving as a drive source. The first tothird fuel tanks 12 a, 12 b, 12 c store, as fuel oils, a vegetable oil,a fatty acid methyl ester, and an A heavy oil, respectively. The blender13 functions as mixing means for mixing fuel oils sent from the fueltanks 12 a, 12 b, 12 c. The engine 14 receives and is driven by the oilmixture mixed by the blender 13. Among the fuel oils, the vegetable oilstored in the first fuel tank 12 a and the fatty acid methyl esterstored in the second fuel tank 12 b are non-heat resistant fuel oils,while the A heavy oil stored in the third fuel tank 12 c is a heatresistant fuel oil. The non-heat resistant fuel oil refers to a fuel oilthat is highly likely to be oxidized and degraded when directly heated,while the heat resistant fuel oil refers to a fuel oil that is unlikelyto be oxidized and degraded when directly heated.

First, a piping structure for supplying fuel oils from the fuel tanks 12a, 12 b, 12 c to the blender 13 will be described.

An upstream end of a supply passage 16 is connected to the first fueltank 12 a, which stores vegetable oil, and a downstream end of thesupply passage 16 is located inside the blender 13. An electromagnetictype first three-way valve 15 is provided in the supply passage 16. Afirst pressurizing pump 17 is located in a part of the supply passage 16that is located inside the blender 13. The first pressurizing pump 17functions as a fuel feed pump. Thus, when the first three-way valve 15of the supply passage 16 connects the first fuel tank 12 a and theblender 13 to each other, the vegetable oil in the first fuel tank 12 ais sent to the blender 13 through the supply passage 16 while beingpressurized by the operation of the first pressurizing pump 17.

An upstream end of a supply passage 19 is connected to the second fueltank 12 b, which stores fatty acid methyl ester, and a downstream end ofthe supply passage 19 is located inside the blender 13. Anelectromagnetic type second three-way valve 18 is provided in the supplypassage 19. A second pressurizing pump 20 is located in a part of thesupply passage 19 that is located inside the blender 13. The secondpressurizing pump 20 functions as a fuel feed pump. A branch supplypassage 19 a branches off a part of the supply passage 19 between thesecond fuel tank 12 b and the second three-way valve 18. The branchsupply passage 19 a is connected to the supply passage 16 with the firstthree-way valve 15.

Therefore, when the first three-way valve 15 of the supply passage 16connects the second fuel tank 12 b and the blender 13 to each other, andthe second three-way valve 18 of the supply passage 19 disconnects thesecond fuel tank 12 b and the blender 13 from each other, the fattymethyl ester in the second fuel tank 12 b is sent to the blender 13through the branch supply passage 19 a and the supply passage 16 whilebeing pressurized by the operation of the first pressurizing pump 17. Onthe other hand, when the first three-way valve 15 of the supply passage16 disconnects the second fuel tank 12 b and the blender 13 from eachother, and the second three-way valve 18 of the supply passage 19connects the second fuel tank 12 b and the blender 13 to each other, thefatty methyl ester in the second fuel tank 12 b is sent to the blender13 through the supply passage 19 while being pressurized by theoperation of the second pressurizing pump 20.

An upstream end of a supply passage 22 is connected to the second fueltank 12 c, which stores A heavy oil, and a downstream end of the supplypassage 22 is connected to the supply passage 19 with the secondthree-way valve 18 provided in the supply passage 19. An electromagnetictype third three-way valve 21 is provided in the supply passage 22.Thus, when the third three-way valve 21 of the supply passage 22 and thesecond three-way valve 18 of the supply passage 19 connect the thirdfuel tank 12 c and the blender 13 to each other, the A heavy oil in thethird fuel tank 12 c is sent to the blender 13 through the supplypassage 22 and the supply passage 19 while being pressurized by theoperation of the second pressurizing pump 20. The fuel tanks 12 a to 12c and the blender 13 are connected by the above described pipingstructure. Therefore, three types of fuel oils (vegetable oil, fattyacid methyl ester, A heavy oil), which are stored in the fuel tanks 12 ato 12 c, respectively, can be mixed in the blender 13 in a desiredcombination by switching the states of the three-way valves 15, 18, 21.

A heat exchanger 54 is provided in a part of the supply passage 22 thatis upstream of the third three-way valve 21. The heat exchanger 54functions as heating means for heating A heavy oil supplied from thethird fuel tank 12 c. The heat exchanger 54 has heat exchanger tubes(not shown) surrounding the supply passage 22. High-temperature water iscirculated through the heat exchanger tubes. The heat exchanger 54indirectly heats the supply passage 22 through heat radiation from thehigh-temperature water.

First and second flow regulating valves 23, 24 and first and second flowmeters 25, 26 are provided at the downstream portions of the supplypassage 16 and the supply passage 19 in the blender 13, respectively.The flow regulating valves 23, 24 function as flow regulating means forregulating the flow rate of fuel oil, and the flow meters 25, 26measures the flow rate of the fuel oil. The mixture ratios of fuel oilsmixed by the blender 13 can be adjusted by individually adjusting thefirst and second flow regulating valves 23, 24 on the supply passages16, 19. The supply passages 16, 19 converge at a position downstream ofthe flow meters 25, 26 to form a combined passage 27 a. The combinedpassage 27 a is connected to an inlet port of an oil mixture tank 27 forstoring oil mixture. The outer wall of the oil mixture tank 27 iscovered with heat insulating material. The oil mixture tank 27 thereforeretains heat of the oil mixture stored therein.

The piping structure for supplying fuel oil to the engine 14 will now bedescribed.

An upstream end of a supply passage 28 is connected to an outlet of theoil mixture tank 27, which stores oil mixture, and a downstream end ofthe supply passage 28 is connected to a first return chamber 30. Thefirst return chamber 30 functions as circulating means for circulatingsome of the oil mixture with the engine 14. A first on-off valve 29 isprovided on a part of the supply passage 28 between the oil mixture tank27 and the first return chamber 30.

An upstream end of a supply passage 31 is connected to an outlet of thefirst return chamber 30. A fourth temperature sensor 55, a thirdpressurizing pump 32, and a viscometer 33 are provided on the supplypassage 31. The fourth temperature sensor 55 functions as oil mixturetemperature detecting means for detecting the temperature of oil mixtureflowing through the supply passage 31. The third pressurizing pump 32supplies the oil mixture to the downstream side. The viscometer 33functions as viscosity detecting means for detecting the viscosity ofthe oil mixture. The downstream portion of the supply passage 31 isbifurcated. One of the bifurcated portions is connected to an upstreamend of a supply passage 36, which is connected to a fuel port of theengine 14 with a second on-off valve 34 and an electromagnetic typefourth three-way valve 35. The other one of the bifurcation is connectedto an inlet of the first return chamber 30 with a third on-off valve 37.

Therefore, when the first on-off valve 29, the second on-off valve 34,and the fourth three-way valve 35 connect the oil mixture tank 27 andthe engine 14 to each other, and third on-off valve 37 is closed, theoil mixture stored in the oil mixture tank 27 is sent to the supplypassage 31 while being pressurized by the operation of the thirdpressurizing pump 32. The oil mixture is then supplied to the engine 14through the supply passage 31 and the supply passage 36. Some of the oilmixture to be supplied to the engine 14 is returned to the first returnchamber 30 by opening the third on-off valve 37 as necessary. In thismanner, the oil mixture is supplied while being circulated.

The supply passage 22, the upstream end of which is connected to thethird fuel tank 12 c storing A heavy oil, is connected to an inlet of asecond return chamber 38 with the third three-way valve 21 and a branchsupply passage 22 a. The second return chamber 38 functions ascircuiting means when circulating and supplying the A heavy oil, as wellas temporary storing means when supplying only the A heavy oil to theengine 14. An upstream end of a supply passage 39 is connected to theoutlet of the second return chamber 38. A fourth pressurizing pump 40 isprovided on the supply passage 39. The fourth pressurizing pump 40supplies the A heavy oil to the downstream side. A downstream portion ofthe supply passage 39 is bifurcated. One of the bifurcated portions isconnected to the fourth three-way valve 35 with a third on-off valve 41,and is connected to the upstream end of the supply passage 36, whichcommunicates with the fuel port of the engine 14 with the fourththree-way valve 35. The other one of the bifurcation is connected to aninlet of the second return chamber 38 with a fourth on-off valve 42.

The operation for directly supplying the A heavy oil to the engine 14will now be described. For example, if the viscosity of oil mixture issignificantly high at the start of the operation of the fuel supplyapparatus 11 due to, for example, a low external temperature, the oilmixture cannot be used as fuel. In this case, the fourth pressurizingpump 40 is operated so as to supply the A heavy oil, which has animproved starting performance. The operation of the fourth pressurizingpump 40 sends the A heavy oil stored in the third fuel tank 12 c to thesupply passage 39, while being pressurized. The A heavy oil is thensupplied to the engine 14 through the supply passage 39 and the supplypassage 36. Accordingly, it is possible to supply only the A heavy oilto the engine. Some of the A heavy oil to be supplied to the engine 14is returned to the second return chamber 38 by selectively closing andopening as necessary the on-off valves 41, 42 provided in the bifurcatedportions in the downstream portion of the supply passage 39. In thismanner, the A heavy oil is supplied to the engine 14 while beingcirculated between the second return chamber 38 and the engine 14.

The third fuel tank 12 c, which stores the A heavy oil, is connected tothe first return chamber 30, which circulates the oil mixture, with asupply passage 43 and a fifth on-off valve 44. When the fifth on-offvalve 44 on the supply passage 43 is open, the A heavy oil is added tothe oil mixture circulated through the first return chamber 30. Thisallows the mixture ratio of the A heavy oil in the oil mixture to beincreased.

The supply passage 36 for supplying the oil mixture or the A heavy oilto the fuel port of the engine 14 is bifurcated into a supply passage 45and a supply passage 46 with a switching valve (not shown) inside theengine 14. The supply passage 45 is connected to the first returnchamber 30, which functions as temporary storing means when circulatingand supplying the oil mixture. The supply passage 46 is furtherbifurcated with a fifth three-way valve 47, which is an electromagnetictype. One of the bifurcated portions is connected to the first returnchamber 30, which functions as temporary storing means, when circulatingand supplying the oil mixture. The other bifurcation is connected to thesecond return chamber 38, which functions as temporary storing meanswhen circulating and supplying the A heavy oil.

Therefore, when the oil mixture is supplied to the engine 14, some ofthe supplied oil mixture is sent to the first return chamber 30 throughthe supply passage 45, so as to be mixed with the oil mixture suppliedfrom the oil mixture tank 27. Likewise, when only the A heavy oil issupplied to the engine 14, some of the supplied A heavy oil is sent tothe second return chamber 38 through the supply passage 46, so as to bemixed with the A heavy oil supplied from the third fuel tank 12 c.Further, the A heavy oil that has been supplied alone to the engine 14can be mixed with the oil mixture in the first return chamber 30 byswitching the communication state of the fifth three-way valve 47 asnecessary.

The control configuration of the fuel supply apparatus 11 of the presentembodiment will now be described.

As shown in FIG. 2, the fuel supply apparatus 11 includes a controldevice 48 that controls the apparatus 11. The control device 48 isconstituted mainly by a controller having a CPU 49 functioning ascontrol means, a ROM 50, and a RAM 51, and a drive circuit (not shown),which drives various devices (such as the on-off valves and thepressurizing pumps). The ROM 50, which functions as memory means, storesfuel maps (see FIG. 3) defining the relationship between the viscosityof the oil mixture and the mixture ratios of the fuel oils at differenttemperatures of each fuel oil (vegetable oil, fatty acid methyl ester, Aheavy oil). The fuel maps include various types of fuel maps defined bycombinations of different fuel oils. Further, the ROM 50 storesreference maps (not shown) of various types each corresponding to one ofthe fuel maps. Each reference map represents the relationship betweenthe mixture ratios and the fuel prices for each combination of the fueloils. The RAM 51 stores various types of information, which is rewrittenas necessary during the operation of the fuel supply apparatus 11.

An input interface (not shown) of the control device 48 is connected tofirst to third temperature sensors 52 a, 52 b, 52 c, which are fuel oiltemperature detecting means located in the fuel tanks 12 a, 12 b, 12 c,the first and second flow meters 25, 26 for measuring the flow rate offuel oils mixed in the blender 13, the fourth temperature sensor 55 formeasuring the temperature of the oil mixture, and a process input device53. The input device 53, which functions as mixture ratio setting means,sets the combination of the fuel oils of the oil mixture, the viscositycondition of the oil mixture, and the initial values of the mixtureratios of the fuel oils of the oil mixture, in a step prior to thegeneration of the oil mixture. The control device 48 receives signalsfrom the first to fourth temperature sensors 52 a, 52 b, 52 c, 55, thefirst and second flow meters 25, 26, the viscometer 33, and the inputdevice 53.

On the other hand, the output interface (not shown) of the controldevice 48 is connected to the heat exchanger 54, the third pressurizingpump 32, which supplies oil mixture, the first and second pressurizingpumps 17, 20 provided in the blender 13, the first and second flowregulating valves 23, 24, and the first to third three-way valves 15,18, 21 located upstream of the blender 13. The heat exchanger 54individually heats the A heavy oil before mixing fuel oils to generatethe oil mixture. The heat exchanger 54 is provided to individually heatthe A heavy oil before mixing the fuel oils. The control device 48separately controls the heat exchanger 54, the first to thirdpressurizing pumps 17, 20, 32, the first and second flow regulatingvalves 23, 24, and the first to third three-way valves 15, 18, 21 basedon signals from the first to fourth temperature sensors 52 a, 52 b, 52c, 55, the first and second flow meters 25, 26, the viscometer 33, andthe input device 53. Accordingly, the temperature of the oil mixturemixed in the blender 13, the combination of the fuel oils in the oilmixture, and the mixture ratio of each fuel oil are controlled.

Next, the fuel maps stored in the ROM 50 will now be described withreference to FIG. 3.

The map shown in FIG. 3( a) is a fuel map of an oil mixture that isgenerated by mixing vegetable oil (labeled as SVO in the drawing) and Aheavy oil (labeled as MDO in the drawing). In this map, the higher thetemperature of the oil mixture, the lower the viscosity of the oilmixture becomes. Also, the higher the mixture ratio of the vegetable oil(SVO) in the oil mixture, the higher the viscosity of the oil mixturebecomes.

The map of FIG. 3( b) is a fuel map of an oil mixture that is generatedby mixing fatty acid methyl ester (FAME) and the A heavy oil (MDO). Inthis map, the higher the temperature of the oil mixture, the lower theviscosity of the oil mixture becomes. Also, the higher the mixture ratioof the fatty acid methyl ester in the oil mixture, the higher theviscosity of the oil mixture becomes.

The fuel supply method of the fuel supply apparatus 11 of the presentembodiment will now be described.

When supplying the oil mixture to the engine 14 as fuel, the fuel supplyapparatus 11 generates the oil mixture through the following steps.Specifically, the fuel supply method includes a fuel oil temperaturedetection step for separately detecting the temperatures of the fueloils, and a heating step, in which, based on the detection result of thefuel oil temperature detection step, only the A heavy oil, which is aheat resistance fuel oil among the fuel oils, is heated such that thetemperature of the oil mixture generated by mixing the fuel oilssatisfies a predetermined temperature condition. The fuel supply methodincludes an oil mixture generating step for mixing a plurality of typesof fuels including the A heavy oil, which has been heated in the heatingstep, thereby generating the oil mixture, and an adjusting step foradjusting the condition for heating the A heavy oil in the heatingprocess in accordance with the viscosity of the oil mixture generated inthe oil mixture generating step.

First, in an initial step that precedes all the above steps, the CPU 49sets the combination of the fuel oils in the oil mixture, the viscositycondition of the oil mixture, and initial values of the mixture ratiosof the fuel oils in the oil mixture based on the signals sent from theinput device 53. Specifically, the CPU 49 sets the viscosity conditionof the oil mixture appropriate for use in the engine 14 of the presentembodiment.

Subsequently, in the fuel oil temperature detecting step, the CPU 49detects the temperature of each fuel oil based on signals sent from thefirst to third temperature sensors 52 a, 52 b, 52 c provided in the fueltanks 12 a, 12 b, 12 c, respectively. The detected temperatures of thefuel oils are temporarily stored in the RAM 51.

Next, in the heating step, the CPU 49 reads from the ROM 50 a fuel mapthat corresponds to the combination of the fuel oils in the set oilmixture. Specifically, as shown in FIG. 3( a) or 3(b), the CPU 49 readsa fuel map that defines the relationship between the viscosity of theoil mixture to be generated by mixing the fuel oils and the mixtureratios of the fuel oils for each temperature condition of the oilmixture. The CPU 49 temporarily stores the read fuel map in the RAM 51.

Subsequently, under the condition of the mixture ratios of the oilmixture set in the initial step, the CPU 49 computes a temperature ofthe oil mixture that satisfies the viscosity condition set in the samemanner, by referring to the read fuel map. While referring to propertiessuch as heat capacities of the fuel oils to be mixed, the CPU 49performs thermal calculation to obtain a temperature of the A heavy oilthat is required to obtain the computed temperature of the oil mixture.Based on the computation results, the CPU 49 controls the temperature ofthe high-temperature water circulated in the heat exchanger tubes of theheat exchanger 54, thereby heating the A heavy oil to a predeterminedtemperature.

Next, in the oil mixture generating step, the CPU 49 switches the valvestates of the three-way valves 15, 18, 21 to generate an oil mixturehaving the combination and mixture ratios of the fuel oils set in theinitial step, and controls the operating states of the pressurizingpumps 17, 20. The CPU 49 supplies to the engine 14 the oil mixture thathas been stored in the oil mixture tank 27 by the operation of the thirdpressurizing pump 32. Accordingly, the operation of the engine 14 isstarted.

Subsequently, in the adjusting step, the CPU 49 detects the viscosity ofthe oil mixture at predetermined intervals after the fuel supplyapparatus 11 and the engine 14 are started. The viscosity of the oilmixture can be detected by two methods. The first method is that the CPU49 detects the viscosity of the oil mixture based on a detection signalof the viscometer 33.

The second method is that the CPU 49 detects the temperature of the oilmixture based on a detection signal of the fourth temperature sensor 55.Based on the detected temperature of the oil mixture, the CPU 49computes the viscosity of the oil mixture by referring to the fuel mapthat has been read in the heating step. Specifically, the CPU 49 firstcomputes the mixture ratios of the fuel oils and the volume of the oilmixture stored in the oil mixture tank 27 based on data obtained bymeasuring at all times the amount of the fuel oils sent to the oilmixture tank 27 through the combined passage 27 a and the amount of theoil mixture sent to the engine 14 through the supply passage 28. The CPU49 computes the viscosity of the oil mixture by referring to the fuelmap based on the computed mixture ratios of the fuel oils in the oilmixture and the temperature of the oil mixture detected by the fourthtemperature sensor 55.

Next, the CPU 49 determines whether the detected or computed viscosityof the oil mixture satisfies the viscosity condition of the oil mixture,which has been set in the initial step.

When a sufficient period of time has elapsed since the operation of theapparatus is started, the piping for supplying the fuel oils has beenheated to a temperature equivalent to the temperature of the fuel oils.Thus, the oil mixture supplied to the engine 14 satisfies the viscositycondition that has been set in the initial step. However, immediatelyafter the operation of the apparatus is started, the temperature of thepiping for supplying the fuel oils is approximately at a roomtemperature, which is lower than the temperature of the fuel oils.Therefore, the temperature of the oil mixture supplied through thepiping is lowered below an expected temperature. Such a drop of thetemperature of the oil mixture can cause the oil mixture to stopsatisfying the viscosity condition set in the initial setting.

The CPU 49 compares the detected or computed viscosity of the oilmixture with a threshold value of the viscosity condition of the oilmixture set in advance, thereby determining whether the viscosity of theoil mixture satisfies a viscosity condition of the oil mixtureappropriate for being supplied to the engine 14.

If the determination is positive, the CPU 49 determines that theviscosity condition of the oil mixture supplied to the engine 14 isappropriate, and continues operating the apparatus while maintaining thecondition for heating the A heavy oil in the heating step.

If the determination is negative, the CPU 49 determines that theviscosity condition of the oil mixture supplied to the engine 14 is notappropriate, and changes the condition for heating the A heavy oil inthe heating step.

First, the CPU 49 computes the temperature and volume of oil mixture tobe added to the oil mixture tank 27 based on the states such as thevolume of the oil mixture in the oil mixture tank 27 computed in theadjusting step. While referring to properties such as heat capacities ofthe fuel oils to be mixed, the CPU 49 performs thermal calculation toobtain a temperature of the A heavy oil that is required to obtain thecomputed temperature of the oil mixture. Based on the computationresult, the CPU 49 changes the setting of the condition for heating theA heavy oil in the heating step. Thereafter, the CPU 49 continues theoperation of the apparatus while applying the changed heating condition.

(1) The present embodiment has the following advantages.

(1) In the initial step, in which the oil mixture is generated by mixingthe fuel oils including the heat resistant fuel oil, the CPU 49 heatsonly the heat resistant fuel oil among the fuel oils, or the A heavyoil, based on the detection results of the first to third temperaturesensors 52 a, 52 b, 52 c for detecting the temperatures of the fueloils. At this time, the CPU 49 heats the A heavy oil such that thetemperature of the oil mixture generated by mixing the fuel oilssatisfies the viscosity condition of the oil mixture set through theinput device 53. Therefore, the viscosity of the oil mixture can beadjusted without directly heating the non-heat resistant fuel oils, thatis, the vegetable oil and the fatty acid methyl ester.

(2) The CPU 49 detects the viscosity of the oil mixture generated bymixing the fuel oils using the viscometer 33. The CPU 49 controls thecondition for heating the heat resistant fuel oil such that thedetection result satisfies the viscosity condition of the oil mixtureset through the input device 53. Thus, feedback control can be performedsuch that the viscosity of the oil mixture is kept in a range of thepredetermined viscosity condition after the fuel oils are mixed.

(3) The temperature of the oil mixture generated by mixing the fuel oilsis detected by the fourth temperature sensor 55. The ROM 50 stores thefuel maps, each of which defines the relationship between the viscosityof the oil mixture generated by mixing the fuel oils and the mixtureratios of the fuel oils for generating the oil mixture of the viscosityfor each temperature condition of the oil mixture. Based on thedetection result of the fourth temperature sensor 55 and the fuel map,the CPU 49 controls the condition for heating the heat resistant fueloil such that the viscosity condition of the oil mixture set through theinput device 53 is satisfied. Thus, feedback control can be performedsuch that the viscosity of the oil mixture is kept in a range of thepredetermined viscosity condition without detecting the viscosity of theoil mixture.

(4) The heat exchanger 54 for heating the heat resistant fuel oil isprovided on the supply passage 22 for supplying only the heat resistantfuel oil. Therefore, since only the heat resistant oil is heated, othernon-heat resistant fuel oils are not oxidized and degraded by heating.

The above described embodiment may be modified as follows.

Instead of adjusting the condition for heating the heat resistant fueloil in accordance with the viscosity of the oil mixture generated bymixing the fuel oils, the mixture ratio of the heat resistant fuel oilthat is heated may be adjusted.

One of the viscometer 33, which detects the viscosity of the oilmixture, and the fourth temperature sensor 55, which detects thetemperature of the oil mixture, may be omitted.

The heat exchanger 54, which functions as heating means, may be locatedin the third fuel tank 12 c, which stores the heat resistant fuel oil.

As heating means for heating the heat resistant fuel oil, a heater thatdirectly heats the fuel oil may be provided.

Instead of being connected to the second three-way valve 18, thedownstream end of the supply passage 22 may be directly inserted intothe blender 13. In this case, additional pressurizing pump, flowregulating valve, and flow meter may be provided in the inserted portionof the supply passage 22.

The fuel maps may be stored in an external storage device and read bythe control device 48 as necessary.

The vegetable oil, which is the fuel oil stored in the first fuel tank12 a, may be, for example, palm oil, rapeseed oil, soybean oil, orsunflower seed oil.

The fatty acid methyl ester, which is the fuel oil stored in the secondfuel tank 12 b, may be replaced by an oil that has a fatty acid methylester composition obtained through the methyl esterification of theabove described vegetable oil, an animal oil such as a fish oil, andedible oil waste of these oils, by an alkali catalyst method or anoxygen method.

The A heavy oil, which is used the fuel oil stored in the third fueltank 12 c, may be replaced by, for example, Kerosene, a light oil, a Bheavy oil, or a C heavy oil.

The fuel oils stored in the fuel tanks 12 a to 12 c may be two or moretypes of oils other than the fuel oils shown above (the vegetable oil,the fatty acid methyl ester, the A heavy oil), as long as thecombination includes a heat resistant fuel oil and a non-heat resistantfuel oil.

1. A fuel supply apparatus comprising: a blender, configured forgenerating an oil mixture by arbitrarily combining and mixing aplurality of types of fuel oils including a heat resistant fuel oil anda non-heat resistant oil; a fuel oil temperature sensor, configured forseparately detecting temperatures of the fuel oils before the blendermixes the fuel oils; a heater, configured for heating only the heatresistant fuel oil among the fuel oils before the blender mixes the fueloils; and a controller, configured for controlling, based on a detectionresult of the fuel oil temperature sensor, the heater such that thetemperature of the oil mixture obtained by mixing the fuel oils becomesa temperature that is set in advance.
 2. The fuel supply apparatusaccording to claim 1, comprising: a viscosity detector, configured fordetecting a viscosity of the oil mixture generated by the blender,wherein, based on a detection result of the viscosity detector, thecontroller controls a mixture ratio or a heating temperature of the heatresistant fuel oil that is heated by the heater, such that the viscosityof the oil mixture is kept in a viscosity range that is set in advance.3. The fuel supply apparatus according to claim 1, comprising: an oilmixture temperature sensor, configured for detecting a temperature ofthe oil mixture that is generated by mixing the fuel oils using theblender; and a memory configured for storing fuel maps each defining therelationship between a viscosity of the oil mixture and mixture ratiosof the fuel oils at each of different temperatures of the fuel oils,wherein, based on a detection result of the oil mixture temperaturesensor and the fuel maps stored in the memory, the controller controlsthe mixture ratio or a heating temperature of the heat resistant fueloil, such that the viscosity of the oil mixture is kept in a viscosityrange that is set in advance.
 4. The fuel supply apparatus according toclaim 1, comprising: a plurality of fuel tanks each storing differentone of the fuel oils; and a plurality of supply passages each connectedto different one of the fuel tanks, wherein the heater is provided inthe fuel tank that stores only the heat resistant fuel oil or in thesupply passage that supplies only the heat resistant fuel oil.
 5. Thefuel supply apparatus according to claim 1, wherein the heat resistantfuel oil is selected from the group consisting of an A heavy oil, a Bheavy oil, a C heavy oil, Kerosene, and a light oil, and wherein thenon-heat resistant oil is selected from the group consisting of avegetable oil and biodiesel fuel.
 6. A fuel supply method comprising:fuel oil temperature detecting step including separately detectingtemperatures of a plurality of fuel including a heat resistant fuel oiland a non-heat resistant oil; heating step including heating only theheat resistant fuel oil among the fuel oils based on a detection resultof the fuel oil temperature detecting step such that the temperature ofthe oil mixture obtained by mixing the fuel oils becomes a temperaturethat is set in advance; and mixing step including generating the oilmixture by arbitrarily combining and mixing the fuel oils including theheat resistant fuel oil.
 7. The method of claim 6, comprising using aheat resistant fuel oil selected from the group consisting of an A heavyoil, a B heavy oil, a C heavy oil, Kerosene, and a light oil, andwherein the non-heat resistant oil is selected from the group consistingof a vegetable oil and biodiesel fuel.
 8. The apparatus of claim 2,wherein the viscosity detector comprises a temperature sensor.
 9. Theapparatus of claim 2, wherein the viscosity detector comprises aviscometer.
 10. A fuel supply apparatus comprising: mixing means forgenerating an oil mixture by arbitrarily combining and mixing aplurality of types of fuel oils including a heat resistant fuel oil anda non-heat resistant oil; fuel temperature detecting means forseparately detecting temperatures of the fuel oils before the mixingmeans mixes the fuel oils; heating means for heating only the heatresistant fuel oil among the fuel oils before the mixing means mixes thefuel oils; and control means for controlling, based on a detectionresult of the fuel oil temperature detecting means, the heating meanssuch that the temperature of the oil mixture obtained by mixing the fueloils becomes a temperature that is set in advance.
 11. The fuel supplyapparatus according to claim 10, further comprising: viscosity detectingmeans for detecting a viscosity of the oil mixture generated by themixing means, wherein, based on a detection result of the viscositydetecting means, the control means controls a mixture ratio or a heatingtemperature of the heat resistant fuel oil that is heated by the heatingmeans, such that the viscosity of the oil mixture is kept in a viscosityrange that is set in advance.
 12. The fuel supply apparatus according toclaim 10, further comprising: oil mixture temperature detecting meansfor detecting a temperature of the oil mixture that is generated bymixing the fuel oils using the mixing means; and memory means forstoring fuel maps each defining the relationship between a viscosity ofthe oil mixture and mixture ratios of the fuel oils at each of differenttemperatures of the fuel oils, wherein, based on a detection result ofthe oil mixture temperature detecting means and the fuel maps stored inthe memory means, the control means controls the mixture ratio or aheating temperature of the heat resistant fuel oil, such that theviscosity of the oil mixture is kept in a viscosity range that is set inadvance.
 13. The fuel supply apparatus according to claim 10, furthercomprising: a plurality of fuel tanks each storing different one of thefuel oils; and a plurality of supply passages each connected todifferent one of the fuel tanks, wherein the heating means is providedin the fuel tank that stores only the heat resistant fuel oil or in thesupply passage that supplies only the heat resistant fuel oil.
 14. Thefuel supply apparatus according to claim 10, wherein the heat resistantfuel oil is selected from the group consisting of an A heavy oil, a Bheavy oil, a C heavy oil, Kerosene, and a light oil, and wherein thenon-heat resistant oil is selected from the group consisting of avegetable oil and biodiesel fuel.